1. Field of the Invention
The present invention generally relates to implantable medical leads, and in particular to an implantable medical lead that allows detection of lead insulation damages following implantation and to a method of detecting such a lead insulation damage.
2. Description of the Prior Art
Today implantable medical devices (IMDs), such as pacemakers, cardioverters and defibrillators, among others, are typically connected to heart or nervous tissue by means of one or more implantable medical leads. These implantable medical leads provide electrical contact between the tissue and the IMD, which is generally implanted some distance from the target tissue to be sensed, paced or otherwise treated by the IMD.
The implantable medical lead is a vulnerable component of the IMD system and it can easily get damaged by inappropriate handling during implantation with serious consequences as a result. It is also a well known fact that the hostile environment of an implanted medical lead in addition to the implantation technique used at implantation may cause adverse events debuting later on in time. Illustrative examples include subclavian crush phenomena, conductor breakages, lead insulation damages and various types of lead abrasions.
Symptoms of lead damages may vary from cosmetic to hazardous ones. What they all have in common is that their symptoms mostly debut intermittently, progress gradually and are often very difficult to diagnose due to lack of appropriate tools.
Today the analysis of potential lead damages are performed by analysis of X-rays, intracardiac EGM (IEGM) and lead impedance measurements in combination with lead provocative movements. However, it is very hard to detect small lead damages, such as minor ruptures to the insulation material of the implantable medical lead using prior art techniques. Furthermore, IEGM and lead impedance measurements are not specific tools in order to consistently diagnose lead damages since they are generally not sensitive enough. It is therefore very hard to discriminate between lead insulation damages and other symptoms from IEGM and lead impedance measurements.
Lead damages might cause inappropriate therapy, such as high voltage defibrillation, or inhibition of therapy, such as inhibition of pacemaker pulses. It is therefore important to find an easy, cheap and reliable way to detect and verify lead damages before they create discomfort or injuries to the patient.
U.S. Pat. No. 7,532,939 discloses an active fixation medical lead having a tracking member extending from the distal end of the lead body, through the helical fixation member and outward from the distal end. The tracking member is used to facilitate tracking of the medical lead during implantation. After implantation a radio-opaque solution can be injected through the lumen of the medical lead to thereby leak out of the distal end. There the radio-opaque solution causes residual staining of the surrounding tissue and thereby facilitates fluoroscopic imaging at the implant site.